Laser-based distance and range measuring equipment have been used for a number of years to provide extremely accurate distance measurements to a remote target or object. A representative instrument is the Criterion.TM. 100 laser range finder developed and marketed by Laser Technology, Inc., assignee of the present invention. Although a highly accurate and reliable device, its great distance ranging capability and inherent complexity translates to a manufacturing cost and form factor most suitable only for certain specific applications.
Distances are determined by calculating the time of flight of a laser pulse from the instrument to the target and back and this elapsed time measurement is referenced with respect to a signal from an optical pick-up sensor mounted in the laser transmission path.
While these distance measuring and ranging devices have conventionally used laser diodes for generating the light pulses from which the distance and range measurements are derived, laser diodes are generally expensive components, costing approximately $7.00 to $50.00 depending on the type and quality of the laser diode.
However, while distance measuring and ranging instruments require a high degree of predictability in the optical pulses which they use to derive distance and range information, LEDs have the inherent problem of a variable delay time between the drive current and the optical output dependent on the magnitude of the drive current and the temperature.
A need therefore exists for a range finder which can be economically manufactured as a light weight, rugged and compact unit to nevertheless provide extremely accurate distance measurement capabilities across a wide range of potential applications.